The invention relates to an elevator installation with at least one shaft, in which at least two cars disposed one above the other can be made to travel up and down, the shaft having a plurality of shaft doors and the cars respectively comprising at least one car door, and with a safety device for blocking the travel of the cars when the shaft doors or car doors are open.
The invention also relates to a method for controlling an elevator installation with at least one shaft, in which at least two cars disposed one above the other can be made to travel up and down, the shaft having a number of shaft doors and the cars respectively comprising at least one car door, and it being possible for the travel of the cars to be blocked by means of a safety device when the shaft door or car door is open.
In the effort to increase the handling capacity of elevator installations, it is proposed in U.S. Pat. No. 1,973,920 to make two cars travel up and down in a shaft along a common traveling path. The elevator installation has in this case a safety device, with the aid of which it can be ensured that the travel of the two cars is blocked if a car door or a shaft door is opened. For this purpose, monitoring elements which form series-connected switching contacts are disposed at all the shaft doors and car doors. If one of these switching contacts is opened on account of a shaft door or car door being opened, the supply voltage to both the cars is interrupted and consequently their travel is blocked.
In the case of the cited elevator installation, the lower car is carried on the upper car. This has the consequence that both cars stop simultaneously and start up again simultaneously. If a car door and a shaft door are opened for the loading or unloading of a car, the travel of both cars is blocked by means of the safety device coming into use; since, however, both cars carry out a stop simultaneously, this blockage has no influence on the traffic flow of the elevator installation.
There are also known elevator installations in which two cars can be made to travel up and down independently of one another in a shaft. In the case of such a configuration, it must be ensured by a suitable mode of operation that both cars can be braked and stopped if even only one car is to be loaded or unloaded, since otherwise, when the car door and an associated shaft door of one car open, an emergency stop would be triggered in the case of the other car on account of the safety device coming into use. This would have the consequence of a considerable risk of injury to the passengers of the other car. The stopping of one of the cars consequently leads to hindrance of the travel of the other car. This ultimately has the consequence that the transporting capacity of the elevator installation is restricted.
It is an object of the present invention to develop an elevator installation and a method for controlling an elevator installation of the type stated at the beginning in such a way that the transporting capacity of the elevator installation can be increased and the cars hinder one another as little as possible.